Electric furnace.



W. N. CRAFTS. ELECTRIC FURNACE.

APPLICATION FILED DEC. 4, 1911.

' Patented Aug. 12, 1913.

INVENT'QZ'\ aha; \wf'r f z BY dwnx' 81/ 6 W ITN E5555 HTT RN EY- I To all whom it may concern:

UNITED STATES.

WALTER N. CRAFTS, OF OBEBLIN, OHIO ELECTRIC FURNACE.

Be it known that'I, WALTER-N. CRAFTS, a

" citizen of the United States, residing at Oberlin, in the county of Lorain and State of Ohio, have invented a certain new and useful Improvement in Electric Furnaces,

of which the following is a full, clear, and exact description, reference being had to the accompanying drawings.

This invention relates to furnaces of the shaft or Hochofen' type, the object of the invention being to provide such a furnace with means for heating the contents by electric induction acting on a fused bath at the base of the shaft, heat from which bat-h, rising in the shaft, causes chemical reactions in the contents thereof.

My furnace may accordingly be constructed as to shape somewhat along the lines of the modern blast furnace, and a blast may be employed or not, as desired, while below the shaft I provide a basin adapted to hold the molten bath, and I provide a magnetic core and a primary winding so positioned with reference to the basin that at least some portion of the bath may be included in the secondary circuit and 'be thereby fused. In

my preferred form this secondary circuit comprises a portion of the bath within the basin and a conductor outside bf the basin, the outside conductor being incompletely annular but forming a complete annular conductor in con'unction with such portion in the basin. T e outside portion of the secondary is preferably below the basin connecting with a lower portion of' the both, as properly cir-.

solid conductor of greater electric conductivity than the portion of the annular secondary within the bath, in which case the j external portion will'not fuse. My prior applicati n #657,270, filed October 28, 1911 shows and claims a furnace employing such external portion of the secondary broadly,

terial in the basin is in clectrlc communicawhether it is fusible or of material not fused. My application #662,822, filed No:

vember 28, 1911, covers the employment of the external portionof different material Specification of Letters Patent.

and not fused. The present application'relates to furnaces of the shaft type including either form of'arranging the secondary.

The drawing clearly illustrates my invention embodied in a shaft furnace having the- PATENT OFFICE." s

Patented Aug. 12, 1913. Application filed December 4, 1911. Serial No. 663,860. I

which it may be tapped without destroying the secondary circuit hereinafter referred to. Above the basin the walls continue upwa'rdly' for some distance and then are arched or'continued inwardly, as shown at 14. Extending upwardly from these arches is the shaft 16 communicating with the basin chamber-through the somewhat restricted opening 17. Near the upper end of the shaft is provided the usual charging bell 18. i The drawing shows also a fan and piping 1.9 for the extraction of furnace gases, and shows a twyer 20, which maybe employed, if do: sired. Extending through the body 10 and beneath the basin I show a pair of incomplete tubes 25 open at their ends. these tubes are magnetic laminated cores 26 connected at their ends byyoke pieces 27 supported on suitable brackets 28. Around the yokes 26 are primary windings 30. In the body outside of the tubes 25 are the sec-. ondaries connecting with the material in the bath, which will now be described.

Occupying In the embodiment shown in the drawing,

and an inner leg 36. The twoinner egs,

however, are preferably merged into one common leg, as shown. The outer and in nor legs having their threeupper ends terminatingat the bottom of the basin, the mation'with the material in the U-shaped pas sageways. a

11 starting my furnace, the passageways may be accomplished either by running in molten metal or by filling the passageways and bottom of the bath with chips or filings. The shaft is charged in the usual manner with ore, coke or charcoal and suitable'flux, as limestone. lVhen the furnace is charged to the desired extent, alternating current is passed through the primary windings. This,

by induction, heats the annular secondaries to the fusing point. The fused material in the bath circulateswith the other material and soon the whole bath is molten. This circulation is increased by having the central leg 36 in the'passageways of different area than the sum of the other two (as shown in the drawings), so that the heating is different and the secondaries bodily circulate.

In operation, the electrically generated heat rising from the molten bath through the mass of material in the shaft causes the carbon of the charge to unite with the oxygen of the ore' and the calcium to unite with the silica and other ingredients of the ore in the usual manner. Accordingly, the molten metal and slag continue to descend into the bath-chamber as new material is supplied at the bell. The slag is tapped oif, whenever desired, through a suit-able slag tap 40, and the molten metal is run out through the tap hole 41. At the end of the campaign the material in the passageways 35 and 36 is runout through thenormally plug ed passageway 42. If desired, a blast may e employed in addition to the electric heat. Such blast may be advantageous, particularly in starting the operation, though it is frequently preferable to have no admitted air.

.My furnace, by obtaining the heat principally or entirely from the induction coils, much reduces the coke or charcoal employed in the shaft, for the carbon need be only sufficient, when no blast is employed, to combine with the oxygen of the ore. -When a blast is employed, it will deliver considerably less air than the usual blast, with corresponding diminution in the carbon which must be supplied to combine with the oxygen of the air. I

My furnace not only may make better pigs, by "reason of the elimination-or reduction of air-oxygen and the consequent reduction of carbon employed, but it may produce steel direct, instead of pig iron, because the molten metal, with a comparatively high carbon content, descending from the'shaft into the bath, may be refined by some of the ore also descending into the bath, the-oxygen of such ore combining with some of the carbon content to leave a resulting metal of proper carbon content for steel.

By reason of the-possibility in my furnace of maintaining the heat without blast, I can eliminate troublesome oxygen or nitrogen compounds which occur with the ordinary blast furnace operation.

Having thus described my invention, what I claim is:

1. In an electric furnace, the combination, with-a shaft adapted to contain material descending by gravity, of an induction coil adjacent to the base of the shaft and having an annular secondary, a portion of which comprises material in a continuous fused bath into which the shaft discharges and the rest of which is below such bath.

2. In an electric furnace, the combination of a basin, a shaft above the basin discharging 'thereinto, and an induction coil having a substantially horizontal closed magnetic core, one or more primary windings therefor and an annular secondary, at least a portion of which comprises material in the basin and the rest of which is below the basin.

3. In an electric furnace, the combination of a basin, a shaft above the basin, means for controlling the entrance to the shaft near its upper end, and an induction coil having an annular secondary, a portion of which comprises material within the basin and a portion of which is exterior of and lower than the basin, the basin being provided with means enabling it to be tapped without destroying the secondary circuit.

4. In an electric furnace, the combination, with a shaft and a basin .below it provided with a tap for metal, of means for heating by electric induction the material'in the bath, the heat rising from such bath into the shaft, said means comprising a substantially horizontal annular core, a primary winding and an annular secondary, a portion of which consistsof molten metal in the basin above the metal. tap and the rest of which consists of a U-shaped conductor not destroyed by the tapping operation.

5 In an electric furnace, the combination, with a shaft, of a basin below it, an induction coil having a' substantially horizontal closed magnetic core, primary windings about the legsiof the core, and an annular secondary composed of a portion of the bath and a multiple U-shaped conductor extending about the primary outside of the bath, said basin pro'vidin a receptacle in which thematerial may co lect and from which it may be tapped without destroying the secondary circuit.

6. In an electric furnace, the combination of a shaft, a basin below the shaft in which the molten metal from it may collect, .a U-

shaped passageway for material below the basin which has its upper ends in communication with the bottom portion of the basin,

asubstantially horizontal closed magnetic core having a leg lying between the arms of said passageway, a primary winding on said core, and means for tapping molten horizontal closed magnetic core having legs metal from the basin without destroying the lying between the arms of the passageways, annular secondary which is provided by the and primary windings for said core sur- U-shaped passageway and a portion of the rounding said legs.

5 molten metal in the basin. In testimony whereof, I hereunto aflix my 7. In an electric furnace, the combination signaturein the presence of two witnesses. of a Shaft, a basin. below the Shaft in N molten metal from the shaft may collect, a

plurality of U-shaped passageways having Witnesses: 10 their. adjacent legs in common and lying in a ALBERT H. BATES,

substantially vertical plane, a substantially BRENNAN B. WEST. 

